How to check a hydraulic estimate before the tender closes

01Start with the documents, not the number

Before you look at a single rate, make sure the estimate prices the right documents:

• Compare the drawings priced against the drawing register. Same sheets, same revisions.
• Check every addendum and RFI response issued during the tender. Late addenda are where scope quietly grows.
• Read the hydraulic specification. Testing, pipe classes, insulation, warranties, work-as-executed drawings and handover documents are written there, not drawn.
• Read the preliminaries and the contract conditions: staging, working hours, liquidated damages, defects period. Each one changes the cost of doing the work.

02The items most often left out

When we check other estimates, the missing money is rarely in the pipe runs. It is in this list:

• Fire-rated penetrations. Collars, wraps and sealant at every service passing through a fire-rated slab or wall, on every level.
• Acoustic lagging on stacks and waste pipes through habitable areas, where the specification asks for it.
• Basement pump-outs. Pits, pumps, rising mains and the interface with the electrical and control trades.
• Sub-soil and seepage drainage behind basement walls, if it sits in the hydraulic package.
• Trade waste. Grease arresters and other pre-treatment, plus the application and authority charges.
• Authority connections. Water main tappings, meter assemblies, sewer junction work, inspections and fees. Confirm who carries each one.
• Backflow devices (RPZDs and testable valves) and their tests at handover.
• Hot water plant: heaters, circulating pumps, thermostatic mixing valves and commissioning.
• Gas: meter, regulator and the authority application, where gas is in the scope.
• Testing and commissioning: pressure tests, flushing, disinfection and drain CCTV, where specified.
• Access: scissor lifts or scaffold for high ceilings and voids, and the extra time in tight basements.
• Fixtures and tapware: supplied by you, by the builder, or carried as PC items? The tender has to say which.

Any one of these can be worth more than the margin on the job. Tick each one off as priced, excluded, or not yours.

03Test the totals against your own history

Once the scope is right, a few quick tests will catch most quantity and rate errors:

• Cost per apartment, per fixture or per square metre against your last three similar jobs. A big difference is not always wrong, but you should be able to explain it.
• The split between labour, materials and plant. If it is far from what your similar jobs look like, something has been missed or doubled.
• Repeat levels. Typical floors should carry near-identical quantities. One level that is very different usually means a counting error.
• The twenty largest lines. Check their quantities against the drawings. They carry most of the value.
• Preliminaries for the programme. Supervision, site sheds and hire plant should run for the time you will actually be on site, not a standard few weeks.

04Read the exclusions like the builder will

The builder will read your exclusions against their own tender. Each one should be specific enough that nobody can argue about it later:

• "Excludes authority fees" is vague. "Excludes Sydney Water connection and inspection fees; includes the tapping work" is clear.
• Every exclusion should match something real in the documents. If the specification puts an item in the plumbing package, excluding it can make your tender non-conforming.
• List your assumptions too: the crew working hours, the number of stages, who provides cranage and hoisting.

05Check the programme and the price validity

• Programme. How many separate visits do staged handovers need? Is fit-off out of sequence because of finishes? Each extra mobilisation is cost.
• Price validity. Copper and other material prices move. State how long your price holds, and whether supplier increases after that are passed on.
• Long-lead items. Hot water plant, pumps and special fixtures can take weeks to arrive. Make sure the programme you priced allows for it.

06A 30-minute check before you submit

1. Drawings and revisions priced match the register.
2. All addenda and RFI responses are included.
3. The specification has been read for testing, materials and handover.
4. Every item on the "often left out" list is priced, excluded, or confirmed as not yours.
5. Cost per unit is compared with three similar past jobs.
6. Repeat levels carry matching quantities.
7. The twenty largest lines have been checked.
8. Preliminaries run for the real programme.
9. Exclusions and assumptions are specific.
10. Price validity is stated.

07When to get a second set of eyes

On a large tender, an unfamiliar building type, or a close date that leaves no time to step back, an independent check pays for itself. We can price the job in full alongside yours and show you where the two numbers differ and why. Send the tender documents and we will come back with a fixed fee and turnaround within a few hours.

08Related reading

• Outsourcing your plumbing estimating: how it works and when it pays
• What to send your estimator: the tender documents checklist
• Fire-rated penetrations: collars, wraps and mastic
• NSW trade waste charges: what to allow
• What should I include in a plumbing estimate?